Peroxycarboxylic acids (also referred to as peracids), as well as mixed peroxycarboxylic acid systems, are known for use as antimicrobials and bleaching agents in a variety of industries. Peracetic acid or peroxyacetic acid (PAA or POAA) (dynamic equilibrium mixture of POAA/PAA, H2O2, H2O and AA) have been used in the food and beverage industries as a fast acting, “green” antimicrobial. Such products demonstrate beneficial properties towards oxidizing solids and improving water quality. In addition, compared to other commercially available biocides, the use of peracetic acid results in a low environmental footprint due in part to its decomposition into innocuous components (e.g. acetic acid (AA), oxygen, CO2 and H2O). See for example, U.S. Pat. No. 8,226,939, entitled “Antimicrobial Peracid Compositions with Selected Catalase Enzymes and Methods of Use in Aseptic Packaging,” which is incorporated by reference in its entirety.
Peracids have also been used for certain water treatment applications. However, these have been very limited in the area of commercial well drilling operations. See for example U.S. Patent Publication No. 2010/0160449, entitled “Peracetic Acid Oil-Field Biocide and Method,” and U.S. Pat. No. 7,156,178 which are incorporated by reference in their entirety. However, particular water treatment applications present difficulties for the use of peracids during several steps of the oil and gas production methods, including for example microbial efficacy and compatibility concerns. For example, despite its fast action and eco-friendly properties, the use of peracids, including peracetic acid, has a number of limitations for use in water treatment methods. High dosages of the peracid can increase the corrosion rates in pipelines and equipment due in part to the presence of hydrogen peroxide (H2O2). Moreover, the peracids/H2O2 can interfere with the activity of functional agents necessary for the methods of water treatment in oil and gas recovery, including friction reducers and thickeners which are often critical for the fracking process. In addition, peracids and hydrogen peroxide are prone to quenching from common, naturally occurring chemicals which can severely limit their utility.
There remains a need for enhanced water treatment methods. For example, from a microbiology perspective, mitigation of microorganisms is essential to minimize environmental concerns for waste products and to avoid contamination of systems, such as well or reservoir souring and/or microbiologically-influenced corrosion (MIC). As a result, prior to the drilling and fracking steps, water is treated to restrict the introduction of microbes into the well or reservoir. This also acts to prevent microbes from having a negative effect on the integrity of the fluids. In addition, before disposal, flow-back water is treated to abide environmental restrictions stipulated by regulatory agencies.
Accordingly, it is an objective of the invention to replace conventional oxidizing biocides for water treatments, such as typical equilibrium peracetic acid, hypochlorite or hypochlorous acid, and/or chlorine dioxide compositions.
It is a further objective of the invention to develop methods for water treatment in oil and gas recovery that provide effective antimicrobial efficacy without any deleterious interaction with functional agents, including for example friction reducers and viscosity enhancers.
A further objective of the invention is to develop compositions and methods for use of atypical peracids via distillation, perhydrolysis of acetyl donors, and preferably use of peroxide-reducing enzymes to improve the stability of peracids and peracid compositions and in most cases the antimicrobial efficacy of the peracid compared to the use of conventional equilibrium peracids alone.
A further objective of the invention is to develop methods using peracids for the treatment of water used in drilling and/or fracking, as well as treatment of water that is planned for disposal to result in cleaner water with low numbers of microorganisms.
A still further objective of the invention are compositions and methods for using peracids, namely peracetic acid, with a peroxide-reducing enzyme such as catalase to reduce and/or eliminate the H2O2 in order to minimize the negative effects of H2O2.
Other objects, advantages and features of the present invention will become apparent from the following specification taken in conjunction with the accompanying drawings.